Aircraft radio apparatus



Oct- 6, 1953 w. K. ERGEN AIRCRAFT RADIO APPARATUS 8 Sheets-Sheet l Filed Oct. l5, 1945 Oct. 6, 1953 w. K. ERGEN 2,654,882

AIRCRAFT RADIO APPARATUS Filed oct. 15, 1945 8 sheets-sheet 2 Oct. 6, 1953 W, K, ERGEN 2,654,882

AIRCRAFT RADIO APPARATUS Filed 061'.. l5, 1945 8 Sheets-Sheet 3 Oct. 6, 1953 Filed OCT.. 15, 1945 W. K. ERGEN AIRCRAFT RADI'HAPPARATUS 8 Sheets-Sheet 4 INVENToR. WML/HM K. E/GE/v Oct. 6, 1953 Y W,A K ERGEN 2,654,882

AIRCRAFT RADIO APPARATUS.

Filed OCT.. l5, 1945 8 Sheets-Sheet 5 LITOP/LOT H Z IMU 7' H FUNC T 10N IN VEN TOR. WILL/HM If. 4Elfllv Oct. 6, 1953 w. KERGEN AIRCRAFT RADIO APPARATUS 8 Sheets-Sheet 6 Filed Oct. 15, 1945 IN VEN T/f WML/17N lf. [/GEN A4 M firm/mn Oct. 6, 1953 W. K. ERG EN AIRCRAFT RADIO APPARATUS 8 Sheets-Sheet 7 Filed Oct. l5, 1945 INVENToR WML/HM lf. flfG/EN.

Hrm/Mfr kif Oct. 6, 1953 Filed Oct. 15, 1945 W. K. ERGEN AIRCRAFT RADIO APPARATUS 8 Sheets-Sheet 8 BYl Patented Oct. 6, 1953 'UNEITIEB .STATES artnr orties .22 (llaims. .1

This invention relates tto 'the iield of `instruments which fprovide 'control for :supervision yof theoperation 50i afcargo releasing aircraft `so that Ti'tsgronnd path and Ythe point at which releaseof the L'cargo takes place may I'be :coordinated with esu'imafol'e radio signals.

It is an object =of the .invention to ,provide :means for :directing .the craft along a rectilinear @ourse from :any :instantaneous locati-on of .fthe Tvcraftto a selected destination, bythe use :of fradio relaying base stations :having known-geographic llocations with :respect ato the destination .and cooperating with radio transmitting and receiving means-carriedibyfthefcraft.

It is :another 'object of the invention to prox/fide Y :means indicating the interval `remaining .before lthe :arriva-lof a craft at its true Ldestination, `or :at `a virtual `destination shaving -a v@redeterlnined relationship with `thetrue destination, by the Vuse -of :the radio equipment above recited.

It =is v-anotlrleroloj ect of the invention .to .provide means .directing the .course `of va craft towards a Jselected destination and .automatically ,perform- -ing .a mechanical Pfunction, .such as releasing `or picking .up cargo, upon arriving at the .destination, by the use of the radio equipment .above recited.

It lis another object .of the 'invention `to. provide dmeans .directing a vcraft along .a rectilinear course xpassing through .a Aselected destination, characterized fby the "fact that the magnitudes of 'the `components of the velocity of .the craft along elinesjoining a pair of'base stations withthe Tse- Llected destination, are Yproportional'to 'the'magnitudes of the projectionaon the'sarne lines, ofthe -distance between the 'craft and its destination.

A more specic object of the Ainvention is to `provide a 'normally energized eleotric'bridgeihav- Aing resistances manually variable in accordance with the magnitudes of the above components of 'the velocity of 'the craft, and lother resistances "variable byinotor means in accordance with y'the magnitudes of Ythe 'above projections, together 'with lmea-ns v'directing the course of `4:the craft "-in accordance with 'the unbalance Vof the 1bridge.

Another specific object of the invention 'is to lprovi'de a -plurality 'of "resistors 4and means *i'or :connecting the 'resistors 'in one or the'otherof v'twofbridges Yhaving the same energizing source 'and the same immediate output circuit, and fior selecting one of 1a ipluralitv ofnltimate controlled l "devices `for 'energization in accordance -with 1un- "balance'ofthelbridge A further specific object of the invention is'to .provide a pluralityof motor 'controlcircuits and fcation two distinct .electric Ybridges shaving 'the :same fenergizin'g :source fand dead minou-it, to'gei';lrer with means for varying thefresistances of certain resistors .in #che 'bridge system simultaneously 'with foperation 'of the Vmotor icontrol Pcircuits, and with inea-ns .for `varying other resistors in :the ylcridge .system :by emotors controlled Joy :the ,motor -fcontrol circuits, .means fleeing also provided :for warying iurther .resistances in fthe :bridge .system ein: ancordance withrornponenta .-in--selecteddirections, :of ia vectorquantity :also having :a selected adirection, and for varyingrafstill further resistor :in the bridge ASystem in accordance with the unrbalancefoffoneioi the bridges.

Various 'other (objects, advantages, v.and -features -of :novelty which characterize my .invention .are pointed aut with ,particularity .in the .claims ,annexed hereto and forming a part hereof. However, ior abetteriunderstandingfof fthe invention, its advantages, and objects attained `Icy its use, .reference should be :had to the vsulojoined drawing, which forms 4a further part hereof, Xand sto the .accompanying descriptive matter, in which there is villustrated and describedapreferredem- In'th'e drawing:

`Figures 1, "2, vand -3 are Vdiagrams illustrative A:of the lbasis of Aoperation ifor 'the invention;

"Figures'flg, 6,'and' 7-arefmechanicallschematics illustrative of the lstructure of the invention;

Figures 8 and -9 'are simpli'edlwiring :diagrams 'of v'bridges Acomprised -in the Iinvention;

Figure 10 1is "a Eblock 'diagram s'lfiowing the in- 'terrelation between Iportions of va fcomplete sys- "tem-'compris'ing the invention;

l`Figure lll 4is fa lschematic f showing of one :of the -nrotor controlsystemsenibodiein thesinvention;

lFigure '12 is ya detailed .wiring diagram 'of she invention;

Figures 113, 114,315,116, L-' .and 118 are wiews .of a vector resolver comprised inithe sinvention, :parts -loeing -isectioned or broken away .to :more ficlearly =discloseithefinvention;:and

Figure 21S-dsa 'detailedfview of switching mechfanism-comprisediin the invention.

"General description A -coinplete system ffor controlling :the :opera- --tion ofarcarg'o releasing aircraft zaccordingtoithe Einvention iis schematically illustrated fin Figure 10, to which reference should now be made. In thegure, ftifs the :automatic ;pilut1oizan aircraft, yfand lmay tbe felectric, fhydranlic, for .of ynther :desired nature. :Aecoursecontrolffunit -iH `is provided iiorzactuatin'g the azimuthfiunctionofthe a-iplurality'o'fvariableresistors'adaptetl'fforiasso- T55 aulmati Ipilot .rby fmeans 'appIQ-Priate to -the structure thereof and is shown as coupled thereto by the means l2 which includes a disengaging member 516. A pilots instrument panel is shown at I3, and is coupled by means i6 to course control unit Il, which is in turn coupled by means i4 to a navigating and computing unit l5 whose manual controls and indicators are schematically indicated. Disengaging member tit is provided so that the panel may be actuated independently of the course control unit.

The craft is to be equipped with a compass as shown at Il, which is coupled by suitable telemetric means 20 to unit l 5 for effecting the operation thereof.V In order to control the speed of motors comprised in unit I5, presently to be described, by operation of control members also comprised in the unit, a pair of variable speed motor controls I8 and 10 are shown at 2l: they are individually coupled as at 22 and 23 to unit l5. A mechanism 24 which may be designed to pick up or release cargo or to perform any other desired function is also shown as coupled, by means 25, to unit I for actuation thereby.

A distance monitor 26 is shown as associated by radio means 21 and 3U with a pair of base relay stations 3l and 32, and a pair of mechanical inputs 33 and 35 are shown actuating monitor 2B under the control of unit I5, through disengaging members IM and 52E. A remote control unit 29 may also be incorporated in the system if desired. The constructional details and arrangements of components Il, i3, l5, and 2l comprise the structural contributions of this invention, but the invention also embraces the combination of these novel members with the remaining components in the complete system and in subordinate combinations thereof.

The navigating function One function of the complete system is to control the automatic pilot of a craft, according to indications of the distance monitor, so that the craft follows a straight line course from its position at any time to a selected destination. It will be appreciated that this function can be l performed equally well for an aircraft or a marine Details of the structure and theoretical operation i of any such monitoring devices comprise no part of the invention, and are therefore not specifically illustrated.

As a basis for a complete understanding of the invention, however, the operation of a generalized radio instrument serviceable as unit 26 will now be described. It must be borne in mind that this disclosure is made only for illustration, and that many monitoring devices with which the invention is well adapted to cooperate will occur to those skilled in the art. For confirmation and additional information relative to the radio principles here disclosed, reference is made to the April and May issues of Q. S. T. for the year 1945.

The purpose of monitor 26 is to give a continuous indication of the distance between the craft in which it is mounted and each of the two fixed relay stations, 3| and 32. This is accomplished in each case by observing the interval between d the transmission of an electromagnetic impulse and the reception of the impulse after retransmission from each relay station: since the speed of propagation of electromagnetic radiation is known, and the relay interval required at the relay station to receive and retransmit the radiation may be accurately determined, the interval observed is a measure of the distance between the station and the craft. The system operates on well known principles briefly reviewed in the next three paragraphs.

The speed of propagation of electromagnetic radiations has been determined with great accuracy tobe 186,284 miles per second: that is, a radiation requires about 51/3 microseconds to travel a mile. A measurement of the interval between the transmission of a pulse of electromagnetic radiation at one point and its reception at another would consequently be a measurement of the distance between the receiver and the transmitter, but involves the impossibility of determining at either station, without time lag, exactly when the function at the other end is performed. This difficulty can be avoided by measuring the time required for the radiation to travel from the transmitter over the required distance and to return, and dividing this time by two, if there is no loss of time at the point whose distance is to be measured. A reflected radiation, such as is used in absolute altimeters, is an example of this system.

It is not usually easy to determine, among all of the reflections of the radiated pulse, which one comes from the point in question. If a radio relay station is established at that point, however, to retransmit the pulse, the retransmitted pulse can be identified by its greater amplitude, and the interval between transmission of the original pulse and reception of the retransmitted pulse, reduced by the relay interval, is a measurement of the round trip distance desired. This procedure is simplified when the relay interval is constant, since it can then be taken into consideration in the original setting up of the instrument, the indication thereafter being proportional to the desired distance.

In a conventional cathode ray oscilloscope tube, it is possible to cause the beam to trace a circle on the screen by applying alternating voltages of the same frequency to the pairs of deflecting plates in phase quadrature: the beam travels around the circle once for each cycle of the alternating or sweep voltage. If the sweep frequency is 93,142 cycles per second, the beam traces its cycle once while a signal pulse of electromagnetic radiation is traveling one round trip mile. Reducing the sweep frequency decimally has the effect of decimally increasing the distance traveled by the radiated pulse in one period of the sweep voltage. If, in addition to the sweep frequency, a voltage pulse is impressed on a suitable electrode by transmission of the signal pulse, and a second voltage pulse is impressed on this electrode by the reception of the retransmitted pulse, the angular displacement about the circle between the traces of the two voltage pulses is a measure of the travel time of the radiation, and therefore of the round trip distance to be determined. The transmitted pulse may be repeated each time the sweep voltage passes through a particular point in its cycle, so that the indication on the screen of the tube appears continuous.

The system requires a pulse transmitter, a pulse receiver, and the indicating oscilloscope in the ineving jtim-it, and a exea 'relay station oh ground Lfor `each l'distance ito `be measured. The Acorobin-ing *to lgive the distance from an arbitrarily assigned first station SI will be rel:ferred vto "as Vpriril'ary fand the other as secondary. 'Operation "of ithe system "depends on observation of the angle between the transmitted and reoeived 'pulses as described a'oove. 1f la phase fs'hifter is provided in the `receiver Ait is possible, by operation of 'the phase ehiitehfte brine the tra'c'e of 'the received zpulse into :alignment with that of the transmitted pulse. Whehthi's condition is reached theamoun-tof .angular displacement of the .phase shifter shaft, from its position when ithe di'sta'rice between the ytransirlitter 'alridthelbasestation Tis vzero, is ameasurement `of 'the round trip distance required, if considered fin com'un'ction with quotient of 93,142 `divided 'by theisw'eep'frequency. Likewise, if a phase shifter shaft :is operated at `such a rate as 'to hold the craft with 'respect Ato the base station.

The navigation problem Before conlneh'ihg "a detailed description of Structures embodying -tlie invention, reference is made to Figures 1, 2, and i3, Ypresent the problem of mensuration which it is desired to solve and show the method by which the solution is accomplished. In Figure l, a craft carrying the distance monitor is located at P1, a first relay station -is located at S1 and a second relay station is located at S2. Here di is the distance l'from the craft `to station Si, `as indicated -by the primary phase shifter .in the distance monitor-henceforth called the primary radio distance. Similarly, da 'is the Isecondary radio ldistance; that Lbetween the craft and the second relay :station: Athe Words primary and secondary are Ato be "interpreted in terms of `rriiitual -distinction rather than in terms of significance or importance.

r Now suppose the craft moves to a new position 4P2: 'there the 'piima'ryra'dio distance *is di 'and the secondary radio 'distance is da". A change n'lP'Qz inthe primary radio 'distance `and a change P'zQi in the secondary Vradio distanceacconrpany the 'change PrPz in the location of the monitor, the points "Q2 and 'Q1 lying on arcs 'h'a'vin'g centers `-si and isz and radii ahaha de', which 'ares eut 'lines 1l1 and laat A1 and B1', all respectively. Suppose the 'craft is moving "towards a deslill'atm TX, 4s0 lOCated that the line Si'TX 'has a magnetic azimuth 'ai *and a length Z1, both of which can be determined from a map 'of :the area to be traversed. Similarly, Vthe magnetic azimuth a2 and the length lz'of the line STx 'can also be determined. Arcs 'having radii SiPz and SzPz may now -be swung from 'Si 'and "S2, respectively as centers, intersecting l1 'and Zz at A2" and B2", res1; 1'ective'ly.V SiAi" is equal in length to SijPu :SrAa 130 S1132; S231' 't0 S2131; and SB'z" t0 S2132.

. ltive: these sectors a-lso are equal.

fs'tant ratio 'of r the values .of "r1 fand arefcoirstanti.

het t fbe 'the time -requiretifor 'the feraitto travel the distance Latthelra'te hr; tha'tis,

One of the assumptions o'n which 'operation of the invention is based 'is that A1A1 'and l" 'B1' are both -eqlal 'to `Z'er'o. Ith'a's been'fou'rlcl by 'trial 'that this assumption vc'a'n'temade without serio'us error, especially where L is small compared with di and d2; 'that is, the .instrument becomes more accurates 'as tar as this factor lis concerned, Vas the destination is approached. On the :basis of this assumption This is vva condition =for movement fof the craft along a straight line from its location -Pi to ythe 'destination TX, and 'itfmay Ybe show-n that for no other course from Pido'es this equation hold.

It should of 'course 4be realized A'that the foregoing analysis fis true for vany point P taken anywhere around and refers to rectilinear lmotion of the Tcraft at ;a constant fs'peed from 'the particular point P `to Tx. The point `P may be either within or without the angle -t=`s1rxs2 and may even be on the other side of Tx from stations S1 and 'Since piek-d1 it'has `negative values Ifor points A or B on the other lside of TX from Si and p2 has negative values 'for lpoints lA or B on the other side of V"JZ'X ron'frSz. The space about "Tx vm'ay be divided into 'four unequal sectors, -as indicated `in the g'ure by line's andl'".V In sector 1, 'both p1 and jpg Iare positive, 'and 4in'se'c'tor 3 'both p1 and p2 are negative. These sectors are equal. "In sector 2, Ap1 Iis positive and 'pz is negative, While in vsector 4 p2 is vpositive and p1 -is nega- An instrument for making use `of the principle here enuncia-ted in its broadest fashion Imust therefore fbe provided with reversing lmeans to be resorted yto as the craft travel toward the'destina-ti'on'throug-h different sectors.

In the forego-ing discussion, it was fassumed 'that the 'medium through which the movement -a Wire Vlet down from the plane, or to release cargo-carrying units wfrom a Ahigh altitude Vso that their trajectories will carry them into suitable shock absorbing receivers, iit .becomes necessary for the craft to pass, not directly over the true destination, but in a particular direction through a particular point, the virtual destination, whose location with respect to the true destination can be determined. 'Ihus it will be appreciated that for any particular configuration of cargo carrier, such for example as a streamlined cylinder dropped from an aircraft in uniform rectilinear flight, there is a displacement, even in still air, between the point on the earths surface at which the carrier descends and the point on the earth's surface directly under the aircraft at the instant of impact. The magnitude and direction of this displacement, which will be referred to as the trail distance TR of the carrier, are affected by the altitude from which the carrier is released, the speed of the aircraft, `and the magnitude and direction of the wind.

It is now well known that the point of impact of any object dropped from an aircraft in uniform rectilinear flight lies in the vertical plane containing the longitudinal axis of the airplane at the instant of impact, regardless of the direction and velocity of the wind through which the aircraft is flying. It is also known that for any particular configuration of falling object, the distance between the point of impact and the point under the aircraft at the moment of impact, land the time required for the object to complete its fall, are determined by the air speed and altitude of the craft releasing the object and `may be presented in tabular form. The trail distance and the time of fall of such a body are included among what `are referred to as its ballistic characteristic.

The problem is illustrated in Figure 2, in which an aircraft is assumed to be located at Px and it is desired that a cargo carrier be dropped on the point Tx: there is to be found a rectilinear course from Px passing through va point T' such that for a particular altitude and air speed of the aircraft, the trail distance TR of the carrier terminates on point Tx. This may be accomplished in the following fashion.

The magnitude and direction of the wind may be determined either by radio information from a ground station or independently by the observation of the drift angles when the craft follows a pair of courses whose bearings make a ninety degree angle, as is well known. About the point TX on a map strike off a circle having a radius equal to the trail distance TR of the body for the proposed altitude and air speed, on the same scale that PxTx represents the distance of the aircraft from the point TX. Now take a new scale such that the radius of the circle is equal in magnitude to the proposed air speed to be maintained, and at this scale mark off backwards from point Tx the wind vector TTX: a line from Px passing through T" intersects the circle at such a point T that T"T'Tx is the familiar wind triangle. The magnitude of TR is usually very small compared with the magnitude of PXTX, and the plotting of such a course as described above involves inaccuraciesin reading the angle TPXTX, which is very small. The present invention however embodies means referred to as a trail resolver for performing this function mechanically.

It is now apparent that the navigation problem as regards station S1 and S2 is not directing the aircraft to pass over Tx but directing it to pass over T in the direction PXT. This is accomplished as is shown in Figure 3, in which the points Si, S2, P. T", T', yand Tx have the same meanings as already ascribed to them in Figures 1 and 2. The aircraft is to be flown over point T', which is displaced from Tx by the distance T'TX.

The instrument has means as described below for altering the effective value of p1 by the component TR1 of TR(:TXT') along the line 11, which is MTX, and for altering the effective value of p2 by the component TR2 of TR 'along the line 12,Y which is NTX. The effective primary and secondary radio distances corresponding to T are therefore SiM and 82N, or

11-1VITX and lz-l-NTX respectively. However, if arcs having these radii are struck from the respective relay stations as centers, the arcs intersect not at T but 'at some other point T. The second approximation underlying use of this instrument is the assumption that T and T are coincident. In practice, TXT' is so small compared with 11 and 12 that no perceptible error is observed in the practice of the invention, and in order to make the discrepancy evident at all it was necessary to show S1 and S2 many times closer to Tx than would ever occur practically.

The reasoning leading to Equation (1) may be applied as follows to movement of the aircraft toward P instead of toward Px, the specified This is a condition for movement of the aircraft along a straight line from its location at T to the virtual destination T1, and like Equation 1 it is found that only this course satisfies the Equation 2.

Structure of the navigating component Mechanical schematic showings of the structure provided in the invention to set up and maintain the condition represented by Equations 1 and 2 comprise Figures 4 and 5 of the drawing. Figure 4 is symmetrical, primary elements on the right of the vertical center line actuating the primary phase shifter whose function is associated with the primary radio distance and comprising a p1 mechanism 9, and secondary elements on the left of the center line actuating the secondary phase shifter whose function is associated with a secondary radio distance and comprising a p2 mechanism |39.

In Figure 4, a manual adjustment knob 34 actuates a gear 3E which in turn meshes with a second gear 31 carried on a shaft 40. Shaft 40 drives a second shaft 50 through a reversing gear mechanism 4 I the drive being reversed by operation of a reversing lever 42 actuated by a shaft 43 for operation by a manual knob 44. Knob 44 carries an index 45, moving between fixed graduations 46 and 41, the former identifying forward or direct drive through the gear mechanism and the latter indicating reverse drive. Shaft 50 actuates a pair of variable resistors 5I and 52, the former being a rheostat and the latter a voltage divider or potentiometer. Rheostat 5l is connected in an electric bridge system, presently to be described7 by conductors 53 and 54. Potentiometer 52 is connected in a motor control system 59.

9 which; will be referredto as. theri system, by conductors55, 5.6i, 5.1 andi. System 59. is illustrated in, Figure l1, in which potentiometer 5.2- is shown; to have a slider 63 and a winding 64. Conductors 55.and 51 are connected to the terminals. of winding 64. andv energize it with constant unidirectional voltage from a source 63 in such fashion thatthe upper terminal of the Winding is posi tive. Source 56 may be a battery or the regulated output. of a conventional rectifier and` filter. Conductor 56 connects the lower or negative tere minal of winding 64 with the grounded input terminal 61 of variable speed motor control 1llwhose other terminal 1| is connected by conductor 12 with one terminal of a direct current generator 62 conductor 6|! connects the other terminal of generator 62 with slider 63. By these connec-A tions, the voltage impressed between terminals 61 and 1| is the sum of the generated voltage and the. potential difference between slider 63 and conductor 51 resulting from displacement of the slider from its lowermost position. The output voltage of generator 62 depends on the speed at which it is operated, and the magnitude of theV voltage'provided by source 66 may be so. chosen that a suitable position of slider 5.3 on winding SLi introduces into the circuit a voltage which is equal and opposite to that produced by the generator at any given speed of operation. It will be seen that the above recited arrangement provides means giving electrical response to departure in the speed of the generator from a predetermined value at which the output o-f the generator equals the voltage due to the particular setting of slider 63. The voltage between terminals 61 and 1I is accordingly a reversing voltage, depending on whether the speedof the` generator 62 is greater or less than that desired.

Motor control is shown to comprise a. vibra` tor 19 including a winding 18, a vibrating contact 13, and a pair of fixed contacts 14 and 15. Winding 18 is energized from a secondary winding 15 of a transformer 11 having a primary WindingY 80 which is energized from a suitable source 8| of alternating current through a. circuit which may be traced through conductors 82, 83,` 84, and 85 primary winding 80, and conductors 91,' 98, and 81. Energization of winding 18 is eifective in conventional fashion to cause vibrating arm 13- to move back andforth between its fixed conf tacts at a speed determined by the frequency of source 8|. Fixed contact 15 is grounded as at 92: fixed contact 11i is connected with input terminal 1| by conductor 93. Vibrating contact 13. is connected by conductor 96 to one input terminal 94 of an amplifier S5: the other terminal 91 of amplifier 95 is grounded. Operation of vibrator 19y when energized from source 8| is thus effective to alternately impress between terminals Sli and 51 a voltage equal to the sum of the generator and potentiometer voltages and supplied toV input terminals 31 and 1|, and to shortcircuit the amplifier terminals so that there is no voltage between them. This operation is in every respect analogous to the conventional vibrator power supply, except that instead of being impressed on a power transformer to provider high voltage, the vibrator voltageis impressed directly on the input of an amplifier.

Amplifier 95 is provided with heater energization from source 8|, and with plate energization through conductors Il'lti` and from a power supply |012 of conventional construction which is also energized from source 8;|. The function of amplifier 95- is to provide at its output terminals |.|.'|,3.and Milian. amplified voltage of the same. wave form as that impressed upon its input terminals, that is, pulsating voltage having maxima and minima either in phase withthe. source 8| or 180 out of phase` with it, depending upon whether the generating voltage or the potentiometer voltage applied to the vibrator is the larger.

The output. of. amplifier 9 5 is impressed on the input. of a phase` discriminator 99 by conductors H15. and |06. The discriminator is energized from source 8|y and its` output conductors |01 and III! energize one phase of the split-phase motor 6| with ay periodic current having the same. phase as^ that sent to the. dis.criminator.v The other winding of. motor 5|. is. energized from source 8 I, through conductors 8.2; H2, and 9|, condenser 86 and, conductor III.

Motor 6| is constructed and connected, in a fashion well known to those. skilled in the art, so. that, it operates in a, first or forward direction when the voltages energizing the two windings are in phase quadrature in a first sense, and, inl a second or reverse` direction when the. voltagesk energizing the two windings are in phase quad-I rature in the` opposite sense. When only one of the windings is. energizedy themotor acts as a brake on the. rotor shaft.

Shaft. I.|.3. of motor 6i is. connected in driving relationship to generator 62, and. also, through a. gear box Hit. if necessary, with one shaft ||5 of a dierential H6. The secondv shaft |2.| of differential H5. moves the slider |22. of a. rheostat |23 along itswinding |24, changing. the resistance of the rheostat effective between its leads and |26.. The rotation, of a. third shaft ||1of differential H6. is opposed by a friction means H8.v Shaft ||1, is extendedy to. perform other functions more clearly shown in Figure 4,. towhich reference should now again be made.

In Figure 4, shaftv |11 is shown to pass through second reversing gear mechanism |21- having an actuating lever i3d connected to the same shaft 5.3. as. that driving lever 4.2,v and to carry on its outer end a knob |20. For the sake of simplification all gear reductions other than differential gearing have been omitted from Figure 4, with the exceptiony of certain power transmission arrangements, tothe input of one of which, |3|, a shaft is connected which is` operatively connected to, and revolves with` shaft |2| andI hence bears the same reference numeral. Rotation of shaft |2| is. transmitted through unit i3! in the form of rotation of further shafts |32, |33, and |34.

Shaft |32 operates a mechanical counter |35. Shaft |33. is connected through a third reversing gearing |36, a shaft |31 and suitable mechanical coupling and release means |44 to the shaft 33 of the primary phase shifter. Reversing mechanism $3.6 is actuated by a reversing lever lei) connected to the same shaft d3 as are reversing levers. and 4.2. Operation of knob all. is therefore effective to reverse the directionY of. movement of the sliders of rheostat 5| and potentiometer 52 for a given rotation of knob 34, to reverse the direction. of rotation of input shaft ||1 of differential lit for a given direction of; rotation of knob. |2El, and to reverse the direction of rotation of the phase shifter shaft 33 for a given direction of rotation of shaft |33. Knob. dit is to. be in its forward position when the craft is approaching its destination TX in either. the first sector or the second sector, and is to be turned to its reverse position when the craft is approaching its destinationv in the third sector or the fourth sector. Shaft |34 comprises one of the mechanical inputs to a further differential |4I.

The members thus far referred to by the numerals 34 to |40 inclusive comprise the primary radio distance or p1 mechanism, which has been identified by the numeral 9. Each of these components has its exact counterpart in structure and function in the p2 mechanism which is identified by the reference numeral |39. The second mechanism need not therefore be considered in detail at the present time although reference will be made to certain of the elements later.

There remains for present discussion in connection with Figure 4 only the further structure associated With differential |4I. As previously pointed out, the rotated position of shaft 33, when the pulses of the primary oscilloscope are in alignment, is a measure of the distance from the aircraft to base station S1, and since I1 is constant it is possible by proper selection of gear ratios to construct counter |35 to give a continuous indication of p1. Similarly, a counter 52|] in the p2 mechanism may be constructed for operation concurrently with shaft 35 to give an indication of p2. A shaft |38, analogous to shaft |35, and connected to counter 520 and secondary phase shifter shaft 35, provides a second mechanical input to differential HH, and the output shaft 142 of the differential is connected to operate still another counter |43. Since counter |43 is influenced jointly by the factors operating counters |35 and 520, the indication of counter |43 is an approximation of the straight line distance L to the desired destination: the approximation is not exact since the angle varies, but it serves to give a rough idea of the distance L, and its accuracy increases as the aircraft approaches its destination.

Figure schematically discloses a trail resolving mechanism generally referred to by the reference numeral |50, intermediate gearing being omitted. As pointed out above, the trail distance of a body falling from an aircraft in sustained rectilinear motion is in the vertical plane including the longitudinal axis of the aircraft at the moment of impact, and for any particular configuration of carrier its magnitude can be determined readily from tables. A counter |5| has an operating shaft |52 and is adjustable by means of a manual knob |53 to indicate the value of trail thus determined: then the amount of rotation of shaft |52 is a mechanical measure of the trail distance. Knob |53 may bear a scale |18 moveable with respect to a fixed index |19. The extension of shaft |52 beyond counter |51 acts through a mechanical transmission |54 to insert a rst mechanical input into each of two resolving differentials |55 and |56 by means of shafts |51 and |60. Differentials |55 and |56 receive second mechanical inputs through means |58 and |59. The detailed structure of the differentials will be set forth in the discussion of Figures 13 to 17; at present it is sufficient to say that the function of each of these differentials is to cause rotation of an associated rheostat to an extent proportional to that component of the trail distance of the carrier having the direction of one of lines S1Tx and S2TX.

The mechanical outputs of differentials |55 and |56 comprise shafts 16| and |62, which actuate rheostats |63 and |64, respectively. The rheostats are provided with electrical conductors |26, |41 and |48, 406 for connecting them in electrical circuits presently to be described.

It will be appreciated that in flying to different destinations the angle between the lines SiTx and SzTX will be found to vary, and means for adjusting the effect of a change of this angle on the instrument must be provided: such an adjustment is brought about by manual operation of a knob |65, Whose shaft |66 provides a first mechanical input to a differential |61. A suitable index |1|i and scale |1| may be provided so that the proper position of knob |65 may at all times be maintained.

It will also be apparent, the wind vector being essentially constant for any particular approach to a destination, that any change in the direction of the air speed vector changes the whole wind triangle. This means that some sort of a device must be provided to correct the instrument for any change in the heading of the aircraft, and a basis for making this measurement is found in the magnetic heading of the aircraft at any time and the magnetic bearing of the destination from one of the relay stations, S1. A knob |12 is provided on a shaft |13 which gives a mechanical input to a differential |14, and a scale |15 is moved with respect to an index |16 to give a reading of the angle a1 in Figure l. A second input from the repeater |11 of the magnetic coinpass |1, to which it is connected by any suitable telemetric means 25 is also fed into differential |14 by a shaft |82. The output of differential |14 is fed through a shaft |83 to comprise a second mechanical input to differential |61. Mechanical output is derived from diierential |61 by means |58 and |59 already identified.

Structure of the trail resolver For a detailed description of the trail mechanism just described generally, reference is now made to Figures 13, 14, 15, 16, 17, and 18, in which elements identified in Figure 5 bear the same reference numerals. The device comprises a means for determining mechanically, Within its limits, the length of the projections, on two lines having any angular relationship, of a third line of variable length having any angular relationship with one of the first two lines. As applied in the present application, the device determines the length of the components, along lines joining the base stations with the destination, of the trail distance of the cargo carrier measured in the direction of the longitudinal axis of the aircraft.

Figure 18 is a front elevation of this component of the invention, and Figure 13 is a bottom view of the same structure, parts being shown in section or broken away to more clearly disclose the invention.

In Figure 13, knob |53 is provided for setting the magnitude of the trail distance along the axis of the aircraft, knob |65 is provided for setting into the mechanism the angle between the two lines from the stations to the destination, and knob |12 is provided to set the mechanism for the magnetic bearing of the line joining the first base station with the destination.

The structure of the mechanism centers around a housing 260 having a removable side wall 20|, a fixed side wall 202, front and rear walls 263 and 204, a top 205, and a bottom 266, best seen in Figure 14.

Knob |53 is mounted on shaft |52, which is carried in bearings 201 and` 216 in a boss 2|| which comprises a portion of front Wall 203. Shaft |52 carries a gear 2 l2 meshing With a gear 2 I3 driving counter |5| which does not appear in Figure 13. Shaft |52 is internally threaded for a` portion of' its length as at 214, and engages external threads on a rodk 215. This rodi has an outboard bearing 2|6 which comprises a portion of the housingv 200. A cross-arm 2-|1 is fixed to shaft 2|5 by a pin 225. Reference should' now be made to Figure 15, which is a sectional View taken along the lines |5 |5 of Figure 13. Cross-arm 211 has ani enlarged central portion 22| about which a member 222 is fastened in cooperation with a clamping piece 223 by suitable machine screws 2.24. The extremities of member 222 are machined to be received inand fastened to miniature antifriction bearings 226. rThese bearings engage the surfaces of flanges 23.6 and' 22T extending along the top and bottom, respectively, of the housing. Members 211 to 230 cooperate to prevent rotation of shaft 215 about its axis, while permitting it to slide freely in a direction parallel to its axis.

Mounted in a suitable bearing 23|' in wall 262 of housing 262 is a hollow shaft 232 carrying on its end external of the housing a spur gear 233 and on. its end internal of the housing. a relatively large disk 234 having gear teeth. 235. around its periphery. An annulus 236 of friction material iS provided between disk 23.4 and housing wall2|l2 so that considerable mechanicaleffort is required to cause rotation of the disk. In disk 234. there is formed a rectangular mortise 238, having a raised ledge 231 extending along the bottom on one side. Ledge 231 acts as one side of a track for a carrier 240, and an adjustable member 24|. forms the other side of the track and also has a shoulder for holding the carrier in the track: a separate member 242 cooperates with ledge 231 to restrain the carrier Within. the track on the other side. of the mortise. Member 242 is supported on ridge 231 by` suitable machine screws 243, and member 24| is adjustably fastened to the bottom of the mortise by machine screwsv 244 which pass through slots 24.5'in member 24|, thus allowing it to be moved nearer to or farther from carrier 240 to give proper snug fit therebetween. The structure is also shown in Figure- 14,v which is a sectional View taken along the l-ines- |-4.-|4 in Figure 13 and rotated in, aclockwise direction through 90.

An elongated recess 246 passes completely through. carrier 246. A rack 24.1 is mounted on carrierv 240, so that its teeth project inwardlyof the recess, by suitableV means 250i. A shaft 251- passes through hollow shaft 232; andi through the aperture in carrier.` 24i|,.andbears at its inner end a pinion 252'. It will be observed that the end of pinion 252` is flush with surfaces of rack 241;, cross-arm 2|1, and carrier 242.

Mounted on carrier 246 by suitable machine screws 253 is a yoke member 254. Yoke 254. has an elongated slot 255 piercing it, and is mounted on carrier 240 in such fashion that the axisk of the slot in the yoke member is perpendicular to the axis of the recess in the carrier.. The width of slot 255 is the same as the diameter of the end 256 of cross-arm 2|?, which performs the functionsfof members |51 and |66 in Figure 5.

From the mechanism just describedl it follows that rotation of disk 234y about its axis, the yoke member being held at the center of the disk. brings about equal rotation of hollow shaft 23.2 and solid shaft 25|, and that displacement of yoke member 254 from its central position, while disk 234 is held fixed, is effective to bring about rotation of solid-I shaft 25| without rotating hollow shaft 232. If yoke member 254 is displaced from its centralV position and disk 234i is also 14 rotated, there results rotationof hollcwishaft: 232 to the same.- degree as` that: of: disk. 2314;. and rota.` tion of' shaft: 25.1. to a. degree influenced both. byy the rotation of," disk 23.4:and.- by the displacement of yoke 254.

The. mechanismy identified byI reference. numeralsza2f31 to 256 will be referred to asftlie.` TR2. mechanism. 228; andis duplicated by aTru mech,- anism 229 on the otherside of flanges 221- and; 2-3'0', except thatno friction membery correspond-l ing to member 2.3.6.is. in this case provided. For the purpose of. thepresent' disclosure ity appears sufficient togive specific reference numerals onlyto certain of;v these duplicate members,r including. disk 2517' and. itsY toothed portion 266', which correspond* to. disk. 234? and its toothed portion; 2:35.

Members 23|: to. 2:56 inclusive. comprise a. p0r-l tion of differential |55. as indicated inA Figure 5, and the'v corresponding members including; 251: and 260:- comprise alike portion of differential |56. Before discussing ther remaining portions-of differentials |255 and |156, however; it appears de.- sirable to considerthe: means bringing about rotation of disks 2.3.4' and 2.51.

As shown inligures 13 and 16;,the latter beinga fragmentary enlargement, wall; 2.0.1; istraversed by afurther pair of shafts 26|" and 262, thelatter, being solidr and' contained. within the former which is.hol1'ow; IIoll'1.' vsr'shaft. 26,| is carried in a bushing 263 which hasfa press t: in a mount.- ingV 262, but a snug: sliding -t. in walk 20|. Hol'- l'ow shaft 261| carries external oft wall 2611 a gear 264, while internal' ofwall 2.02' the shaftcarries. a smaller gear comprising means |,5&.0.f'Figure5-, and a bevel' gear 265'.

outwardly, shaft 262 extends: beyondthe end of shaft 26|, passing` part Way'through a sleeve 26.9; within which itterminates. A gear 266 is fastened to shaft 2.62 and sleeve 26.6I byy a pin 26-1. An outboard bearing 21D i's provided, and sleeve 269i traverses abushing: 2:11. in member 2'10; A collar 212 is fastened to sleeve 269 by a pin. 213.-. Itis thus apparent that byremoving pins 261.-' and 213-, sleeve 269': can be drawn to. the right as shown in` Figure 16, thus releasingv all constraint. on shaft 262' outside of wall 20|.. Similarly, byy releasingl the set screw or other means holding gear 264 on hollow shaft.: 26|?, alL restraint on that shaft external? of wall' 20LI is released. By these mechanical' expedients there is provided a simple means for obtaining access to the interior of" housing 2663 wall; 26| being removable by sliding along shaft 261|: when the machine screws 21%8 holdingv the Wal`l^ to the housing are removed. It wilT be realized that means similar to those described are also provided for freeing other shafts passing through the-.wall 261i.

MountingV 264' is: fastened within housingY 200 by suitable means which. may include a machine screw 214. Thus the removal and inspection of the differential disclosed in Figure 16 and about to be described is facilitated.

In Figure 16, the continuation. of shaft 262 internally of the housing andv of member 264 is shown tov extend in driving relation through a spider 215', and to. be received within but not fastened to a secondv bevel gear' 216. The latter bevel gear is carried by a shaft 211 which is supported at one end in a bushing 2807111 member 268, and at the other end in a bushing 28:1 in an outboard bearing 262 fastened to member 226|! by suitable means 283. Since shafts 211 and 262 are coaxial, i-t will be apparent that the projection of shaft 2.62 within bevel' gear 21.61 provides an inboard bearing for-shaft 262'. A gear compris.-

ing means |59 as shown in Figure 5 is also fastened to shaft 211, as by a pin 284. It will be observed that gear |59 meshes with teeth 235 on disk 234 through an idler 292, while gear |55 meshes with disk 251 directly.

Mounted on spider 215 by suitable means such as screws and washers 285 are two further bevel gears 286 and 281, spaced 180 degrees about the axis of shaft 262. Members 26|, 262, 265, and 216 to 281 comprise differential |61 as shown in Figure 5, shaft |83 being coupled to the differential by a pinion 290 acting on gear 264, and shaft |66 being coupled to the differential through a gear 295 engaging gear 266. Gear |58 meshes with the toothed portion 260 of disk 251, and gear |59 meshes with an idler 292 which in turn engages the toothed portion 235 of disk 234.

The remaining mechanism associated with dif ferential |55 will now be described, reference being again made to Figure 13, and includes a further mechanical differential 293 and a gear train 294, together comprising means |6| in Figure 5, and rheostat |63. Externally of wall 292 gear 233, carried by hollow shaft 232, meshes with the first of a pair of idlers 296 and 291. The idlers mesh with one another, and idler 291 engages a second gear 360 having a hub to which is fixed a bevel gear 36|. Shaft 25| traverses gear 295, gear 300, and gear 30| and is received in a bushing 302 in an outboard bearing member 303. Fastened to shaft as by a pin 304 is a bevel gear 305. An externally toothed disk member 306 is hollow in its center, and carries on internally directed radial pins 301 and 308 a pair of bevel gears 3|0 and 3||. Pins 301 and 398 extend through bevel gears 3|0 and 3|| for radial contact with a suitable bearing surface 3|2 carried by shaft 25|. Thus means are provided for rotating disk 306 about shaft 25 Disk 306 drives a pinion 3|3 through a gear train including gears 3|4, 3|5, 3|6, and 3|1 mounted on suitable shafts.

Pinion 3|3 is carried on the shaft |6| of rheostat |63 and supports and drives an insulated arm 32| carrying a pair of rods 322 along which there is adapted to slide a contact carrier 323. Resistor |63 also includes a housing 324 on which there is mounted a drum 325 carrying a winding of resistance Wire 326. Winding326 is comprised of two sets of conductors side by side, first ends of the conductor being connected together as at 330 while the other ends are brought out of the housing to provide the connections to the rheostat as shown at |48 and 406. The circuit through the winding then starts with conductor |48 and goes through the housing, traverses the coil to the opposite end, when the first conductor joins to the second conductor: the circuit then retraverses the core back to the other end, and is connected to lead 406.

Contact carrier 323 carries a metallic contact 33| which is adapted to bridge between the two wires just described, thus short circuiting the portion of the resistance Winding extending from the bridging contacts to the common point of the wires and therefore decreasing the resistance of the resistor by an amount depending upon the displacement of the contact carrier from member 312|. Contact 33| nts between the two wires and moves carrier 323 along its rods 322 as the arm is rotated. Full details of a rheostat of this general nature are disclosed in the copending application of Albert Palya, Serial No. 511,333, filed November 26, 194.3, and the showing of the rheostat is here made rather schematic than 75 16 mechanical since the details of the structure comprise no part of this invention.

A mechanism identical in all respects to that just recited is provided completing differential 55 and connecting it with rheostat |64.

Knobs |53, |65, and |12 are mounted adjacent a panel 332, the latter carrying indices for cooperation with graduations on the various knobs. For instance, as shown in Figure 5, the sloping portion of knob |53 may bear graduations |18 for cooperation with a single index |19 carried by the panel. Knobs and |12 are shown as bearing graduations |1| and |15, and an index carrier 333 suitably fixed on panel 332 is arranged to support indices |16 and |19 cooperating with the graduations on the knob. A braking means 339 of any suitable nature is arranged to releasably hold shaft |66 against rotation except when the brake release lever |45 is actuated.

Outboard bearing member 210 is provided with a pair of studs 334 and 335 which comprise bearings for shaft |66 carrying knob |65 and gear 295 on opposite ends. Shaft |66 is hollow, and is traversed by shaft |16 carrying on its outer end knob 12 and on its inner end a bevel pinion 336 meshing with a second bevel pinion 331. Gear 331 is carried on shaft |13.

As is well known to those skilled in the art, a compass follower is a means for producing be tween two members an angular displacement which is proportional to the displacement of the compass needle from its due north position. This is most easily accomplished by a telemetric system including transmitting and receiving electromagnetic devices, and use of such means is contemplated in the present invention. Thus conductors I8! lead from the transmitting device, and are connected by brushes 340 with slip rings 34| carried on a drum 342 of insulating material. Drum 342 is mounted unitary with the stator of the compass follower motor |11 While the rotor of the motor is connected to shaft |83. The stator, however, is mounted for rotation about the axis of shaft |83 in a housing 343, and rotation between the stator and housing 343 is brought about by the action of gears 344 and 345, the latter being carried on shaft |13. A friction braking arrangement for shaft |13 is shown at 346.

It will be apparent that if, under the iniiuence of the compass, follower |11 is energized to cause the shaft |83 to rotate through 45 degrees with respect to the stator, and if at the same time rotation of the stator under the influence of gears 345 and 344 is brought about in the opposite direction through 45 degrees, the actual resulting rotation of gear 264 is zero, and that any inter" relation between the action of the compass and knob 12, which drives gear 344 through the mechanism previously traced, may be obtained if desired.

Before describing the operation of the trail resolving mechanism described above, the normal condition of the mechanism will be defined. In this condition the compass system is energized: aircraft is heading due north: the line S1Tx is also due north: line SzTx coincides with line S1Tx: member 2 |5 is in such a position that member 256 is coaxial with member 25|: the zero graduations on knobs |12 and |65 are aligned with the zero indices |16 and |10: the zero graduation on knob |53 is in line with the index and counter |5| indicates zero; and the tracks on disks 234 and 251 are parallel to rod 2|5. It will be appreciated that this is a mechanical normal position rather than a practical position since, for

fexampleithe stationsl andSz willnotordinarily been thesamelinein. actual .use of-the device.

' Operation :of .the .trail resolver ySince the-trail resolv-ing mechanism is-a `subv:ordinate `componentof the invention Whichis complete in itself, its. operation will .be .described .now, :to v.avoid .complicating .alater description of the invention as an entirety. `Knob .|.53.is first ..set..at its Zerosposition, in which `cour-iter ISI and scale I'Ibo'thread zero. When .this is. done, lcrosssarm .2|'| .is .aligned l.With .the-.axes of discs l234=-and v'25.1. 'Undertheseconditior-is, resistors |.I3ancl |64..are. .adjusted .to .zero resistance.

vThe initialset up of the apparatusis such 4that -When the craft is. headed due north, so that compass follovvenmotorv .|17 .is .set at .zero degrees, and when knobs Y'IE5-.and .I i2 are. set atvzero also, discs-234..and ',251 are rotated to positions Where carrierjli andthe like carrier on .disc 257| move parallel tchach. other .and to`.ro.d..2 5.

thecrat .changes vfheadinglfrom due north the rotorofcompass follower .motor II'i .is energizedandshaft Y|83 .is rotated. This acts through pin'io'n' 290,.gear.26, .andshafti 26| -to 'drive gear '|58 and bevel pinion '265. The former. gear meshes. with the-teethin. disc 257. directly. The bevelpin'ion .engagesjbevel Vpinions .236 and 28?.: isince. spider2"|5 is held motionlessby shaft 252, due to its interconnection throughgears 255 Aand i195 .':With shaft |166 which is locked by brake 339; rotation of pinions' 285 and A28? causes rotation-of .bevel pinionV .216, .and with it shaft 2H, inthe Oppositefdirection tothe rotation of shaft 1262. This resultsin rotation of gear |59, which `.acts.}throug`h idler v`gear 2921.to engage' the. teeth of disc234. `Int`erposition of the idler introduces another reversal of direction, so the two .discs are actuallypdriven. in lthe same direction. The gear ratios 'and motor drive characteristics. are sochosen that kone degree .of change in the heading ofthe craft results in one rdegree of rotation .of .discs '234 and 257.

.By Areference to `a :map of thetarea to be lflown over;the'ya'lueof angle canbe determined: in

rl'igurel thisangle happens to be 43 degrees. Brake 3339 'isreleased and knob |55 isrotated so'thatindex 'I'Iiljis opposite the43 degree mark on scale vI'II: `v.brake 339 is then'again applied. 'This .rotation of :knob |65 iseffective, through .shaTt"|86,A gears295 and '265, andshaft'? to rotate 'spider "27.5- about the axis of shaft `262. Since Jbevel pinion 216 fixed bytheinterengagement of gear |59, through idlerlfwith idiskdywhich is held^by friction means 23%, rotation' of the spider is veifectiveonly to'rotate .Ibevei 'pinion Y'26.5, gear |158, and :disk V257: the 'gear :ratios Q295:26'5 Yand 1581260 :are so Y'chosen 'that rotation 'of knob' |55 through Vajgvenangle .causes equalangular motion of disk 251.

"In Figure. 1 the bearing of line Sl'Txisfnot north,"but 1'01 'degrees east of" north. `Kno`b |72 vis 'accordingly'.rotated Yuntilg'raduation vIBI on 'its scalel is opposite vindex |76. '.This :acts through shaft 11.3, gearstSS and 337, shaft |33, 'andgearsf' and 31W, to rotate 'thestator of the Vcompass follower. "Electrical energization .from .theftransmitter atthe .compass zactsto maintain 1 the stator vand rotor vin .their same :rotational .relationshinso the rotorV follows .the fstator, `.and as .a result. gear i295 rotates gear .i

andhenceggear IES and .bevelpinion .'r, exact- -ly :asidescr-ibed `in. connection with `change in :the .heading of thecraft. lThe mechanical tra-in from .knob 112 tto `thezgear teeth-on xdisksl and 426|] isiso chosen V.that rotation-.ofknob |12 .through a givenangle `results-in rotation -of `.the disks 1through `the .same-.angle and. .inthe same direction.

yFroma knowledge ofthe configuration of the cargo-..carrier to be released, the proposed airspeed, andthe laltitude from .which .the carrier is to be released, itis possible to determine with .-the..aid vof a table .ottraildistance the value of .-this -factor 4which should be set into the instrument. The various components of the mechanismare .so `selected .that one rotation of .knob |53 isproportionalto a known trail disf.tance,l10.0 feet for .the-.sake of illustration. Then if .the value ,of .traiLOrthe conditions. under which. 'the-ightisto Vbe madelturns out to be 472 feet for example, knob |53 is rotated `until counter .I5-.I 4.indicates .4 Aa.ndgra;.`1uation 72 on the ,scale .of...knob .|53 .is .opposite .ton index. Other :mechanical relationship-s .can of course be vused at will.

Rotation. .otknob '|53 has .the effect .of .displacingmemberQZI'IaWay from its axial alignment With'thelaxisof vshaft 25|,..thusmoving yoke 254 .in .its track.

The effect of. rotation lQteither of .the disks v25?7 and '234, when its associated yoke is displaced from .its centralpostion, takes place in the .-same fashion. Thisoperation -will .be describedin .connection with rheostat |63.

The amount of d-isplacementof yoke .25d from its .centralposition -.is,.pro.portiona1 tothe .cosine of angle..of..the .rotationof disc;.23t land .to the displacement .of cross-arm 2|-`|. vThis yoke displacement istransformed. into rotation of shaft .25| by the .interaction .between Arack 241 and pinionlz: .therotation-ot.shaft.25| vwith respect Ato disk'234, that is-With respect to `shaft 232,-;15 .therefore.proportional to the displacement. of Vyokelli. ..IIoWev-.er,. .thedesired output is a change in resistance of rheostat 16h-neither portion of whichfiscarriedbydisk 234, which it must be remembered has rotated with respect to'the housing. fThek rotation v'ofshaft v*25| With respect to the-housing istherefore-not' proportional tothe' movement of the yoke, the disproportion'vbeing v'due to `the"-rotation lof disk 235i. Means are provided for modifying, -in accordance 'with' the'rotaftionfdisk 234, the rotation of' the 'shaftf|6| "o'frheostat'l63 caused" by rotation of 'shaft-'252.

To f accomplish this-modification, the rotation "ofshaft-ffgl `-is `fed finto'fdiiferentialfli through bevel1pinioni3|l5,Whilethatof`shaft 232, reversed A"by-gears 2% andVZSLfis-*fed into 4the same differ- "ential' throughv bevel Vjpinion'ftt i. 'The resulting 'rotation of disk' is the difference between the rotation'of `pifnion'f252vand disk1234,-and is transmitted-to' `the shaft offrheostat |63 through gear train' v2194.

in the Vproblemi-'on"the ground, kthe station 'Ilinesare" Xed and thetrail direction var-ies with the iheadingf''of'the-aircraft. In the mechanism it is foundfpeasier.tofmaintainuthedirection of the trail member `xed and rotate the station iines i aboutit; -which isithe'jfull .equivalent once 4.the system'hasi been coordinated for true north head-ing land true stationbearing. 'The change in 'angle'between :thei'stati'on .lines and the aircraft 'headingcanithus be`"br.ought about bythe same mechanism and in the samemanner as was 'the change in station'bearing just described. For example, .ifEigurel represents a no-.wind ycon.dition,the7 course- .PTX Lof :the aircraft .is valso itsheading, which isv 58-.'.degrees east of north.

As the aircraft takes that heading, a signal from he compass transmitter causes rotation of shaft |33 of the follower rotor with respect to the stator, which is xed by gears 344 and 345 and friction means 346. This rotation of shaft |93 brings about rotation of disks 234 and 251 until they are both displaced, from their positions for due north heading of the aircraft, by an angle of 58 degrees, adjustment of the resistances of resistors |64 and |63 taking place as described above. The result of this is that within the housing, shaft 2|5 and the tracks on disks 251 and 233 have the same angular relation about the axes of the disks as do lines PTx, SzTx, and SiTx in Figure 1, and continuous operation of the compass maintains this relation as PTX changes direction.

From the above described mechanism, it follows that means have been here provided for varying the resistances of resistors |69 and |63 in accordance with the values of the projections, on lines having the angular relationship of lines SiTX and SzTx, of a quantity having the arithmetic value of the trail for the particular body in question, and having the direction of the heading of the aircraft with respect to the lines just recited.

The basic amount by which the resistors are to be varied is determined by the setting of knob |53, which displaces the yokes and rotates the shafts driving the resistors by rack and pinion action. The basic rotation is modified by rotation of the resistor shafts brought about by rotation of discs 251 and 234, which is accomplished in equal amounts by knob |12 or compass follower .343 and unequally by knob |65. As a result of these modifications, the resistances actually set into resistors |64 and |63 have the same ratio as do the components of the trail distance along the lines SiTX and SzTx in the actual problem.

The navigating bridge Before considering the course-directing aspect of the invention as a whole, attention is directed to Figure 8, which is a schematic diagram of the bridge circuit on which operation of the invention is based, and which has been simplied to more clearly point out its basis of operation. In Figure .8 a resistance bridge B1 is shown as being made up of four resistors, the bridge being energized with alternating current from a transformer T and the unbalance of the bridge being fed to an amplier A. Arms of the bridge adjacent a first bridge output terminal are shown as having the values r1 and rz. Each of the remaining arms of the bridge comprises two resistors, those connected between ri and the second output terminal having the values TR1 and pi and those in the remaining arm having the values p2 and TR2. According to the elementary principles of bridge circuits oi' this type, the bridge will be in balance when the condition prevails, and for all other conditions a signal will be supplied to the amplifier from the bridge, the phase of the signal reversing with reversal in the direction of unbalance of the bridge, as is well known. This simplified circuit should be borne in mind in considering the more complicated circuits of Figure 12 to which reference is now made.

The system is shown to comprise autopilot I9, course control unit and instrument panel |3 (shown in two detached portions for simplicity in the drawing). Portions of p1 mechanism 9 and p2 mechanism |39, aswell as portions of trail resolver |59, are shown, and source 8| of alterhating voltage appears more than once on the drawing rather than multiplying long leads to common member. The 'i mechanism 59 and its comparable r2 mechanism 359 are shown in their proper cooperative relationship with the rest of the instrument.

In addition to the above components, further details most of which have already been given will follow, the invention comprises a regulating network 35|, relays 352 and 351, an amplifier 353, electronic motor control means 349 including electron discharge tubes 354 and 355, motors 356 and 359, a transformer 360, a source 36| of direct current independent of the regulated sources in components 359 and 59, a locking switch 1362, a plurality of knob switches 363, and suitable means connecting the various components into a coordinated instrument.

Relay 352, which extends vertically through the center of the figure, comprises a winding 364 in the lower portion of the figure and an armature 365 operating a plurality of switch arms 366, 361, 319, 31|, 312 and 313 from normal engagement with a first set of xed contacts 314, 315, 316, 311, 389, and 38|, on energization of the relay, into operative contact with a second set of xed contacts 382, 383, 384, 385, 386, and 381: fixed contact 384 is not used. Relay 352 functions, in its normal condition, to complete a normally energized bridge circuit 394 (shown in the left central portion of the figure), similar to bridge B1 in Figure 8, having input terminals 399 and 39| and output terminals 392 and 393.

The vcircuit around bridge 994 may be traced as follows: input terminal 399, -conduc-tor 395, r2 resistor 396, `conductor 391, terminal 392, i resistor 5|, terminal 399, conductors 499 and 49|, fixed contact 316, switch arm 319, conductor 398, input terminal 39|, conductor 492, xed contact 315, conductor 493, terminal 494, conductor |25, pi rheostat |23, conductor |26, TR1 rheostat |64, conductor |41, output terminal 393, conductor |48, TR2 rheostat |63, conductor 496, p2 rheostat 491, and conductor 4|9. p2 rheostat 491 is independently operated by a motor 498 and a knob 499 analogous to motor 6| and knob |29 of control system 59. R2 rheostat 4|9 and r2 rheostat 396 are manually operable by a knob 4|6 analogous to knob 34.

Transformer 369 comprises primary winding 4|| and a plurality of secondary windings 4|2, 4|3, 4|4, 4|5, and 4|6, all on a common core 4|1: the various secondary windings have been placed in various positions on the sheet to simplify the drawing. Primary winding 4| is energized from source 8| through switch 429, conductors 42| and 422, and ground connections 423 and 424.

In the normal position of the relay, secondary VWinding 4|.2 of transformer 369 energizes the bridge 394, one end of the winding being connected to input terminal 399 through a limiting resistor 425, and the other end of the winding being connected to input terminal 39| through a limiting resistor 426, conductor 421, contact arm 361, fixed contact 315, and conductor 492.

Regulating network 35| comprises a pair of potential dividers 439 and 43| having sliders 432 and 433 land windings 434 and 435, the windings being connected in parallel by conductors 436 and 431. Sliders 432 and 433 are connected to terminals 449 and 44| of the regulating circuit. The

rfparallelf-zwindings areszenergizedffromseoondary windingdl 3 and transformer 3.6 mfthrough-limiting resistors 423andn429. "fsliderdrmay `benperable by a :manual .lnob:-448,; if. desired z a slider .Il-32 is arranged for foperationbyna shaftfASS as fwillpresentlybe'set forth.

lAmpliiier-353 is .of 'the typein Which-an ampli- `ned `voltageA is delivered :having substantially .the iphase andV wave iormof the Iappliedvoltage :vsuc'h amplifiers 'are well .knowngrto those `sslsilled .1in the aart. '.Thezginput't'erminals 'of' amp1ier1-35'3aare identied" by numerals.` 442sand f43thei "output terminalsflby-numerals i444 .and `445. Sui-table power supply means are included Vinampli-erS whereby heater; biasfand anode woltagesf-asneedveclware 'derived from source-3 I which -isconnected :to theamplierfas at 44B fand-.441. =Amplier-in puti terminal 443 is 1 grounded fas at Y449.

In .the normal position .of relay 352, ibridge 394 :is connectedtozamplier' IthroughY regulating `circuit@ I rina fcircuit which :may .Ybe traced '.irom .inputterrninal 442 :by: conductor-r450 if switch .arm i313; xedfcontact 38 I conductor 45 I ,r Y'input ter- :mina.1"-440,regulator circuit- 35I outputtermina-l 44| conductor 452,V switchv arm 312,' .fixed contact 380, conductor 453, bridge output terminal.392, -bridgezl394,' output -te1'minal.z393,- conductor-454, 'fix-edi contact'.` 314,.-fswitch arm 355, groundr con- -nections45'5 .and 449 to the :input terminalf443.

- Electronic motorvcontrol means 349 4comprises :a conventional phase vdiscrirninator circuit. :,'Iubes--354f'andv 355 .-arefshown to comprise triodes which have a common :input resistor MII-energized from 1.amp1ier1353. Heating current is supplied ltotubes-t'tand 355Y from la common secondary Winding- 4I4 of rtransiormersl). :Triode 355 com- .prises aa. plate-456mJ .grid v45'1, vafcathode 458- and .ra :heater-filament'459, the latter. being .connected 'tofwin'dngsfM 4. .Cathode :458: is groundedfas :iat 455,*-iandisconnected :to fone fterminal'rof input resistor z 460. Grid `I 51 is connected :to 1 the :other terminalofresistor V'450. .Plate 4.56 is connected to one terminator secondary' winding-i443 of transformer 360 .'by. conductor i448 :therot-lier tern'ninalofthe-.secondary `windingzis connected to cathode' throughone of .ar plurality of circuits :includingfpo-rtions"offrrelay: 352- andfloekingvswitch 3'62uand 1a Ystator `Windingr ofl one or the other-of `xnntorsSiiIi'andi 359. lTriodei541comprises:a plate "45| Va .grid-462,:a cathodet 453,1-andaY heater la- .ment tgthei latter :being connectedL to `-vIz-indng f4 I4. Y.'"Cathode'14153'is'fgroundeol'eas"atL 4'85, and `is connected tto "one" terminal fof -rinput'fresistor r 460. Grid v402 iszconnected :toithez'other-terminal of rninal `fof:fsecon'darywinding 4 I5 foftransformer 513610. Tby conductor' 468 :'vthe .zother "terminal .of-the secondary winding is vconnected to fcathode through :one of a. plurality of :circuitsfincluding .portions of Irelay=352 band lockingsWitch'r'SBZf and -one :orztlie other of motors 356 Iandil351.

.Locking .switchf352 (nfthe 'lowers-:right hand :corner .o'f thejgure), is'lshown to confiprise.;afour- V.pole fdoublethrow: switch'finclucling switchY .farms 4669451 14%,. and 41| ,rfrsti xe'd contacts 4:12,

413,9414, andr-15, and; second .xedp-.contacts'fll 6, 4I'I,VY 480,'iand148 I witl'i'which :the -switch-arms are normally engaged. The switch-,isfactuatednby v a handle Y482 :including-an rindica'torf '483` movable between indices1484 and-:405. "Switcherm 4166 is .groundediasiat 438. -Fixed contacts-4111;and:r4i8.I :aretnot-used Motor 3516 irisfshowni to comprise :.a apairfof iield windings i486- land 481 :and a-squirrelcagefotor P.1100. ."rA-condenserdl isfiniseries withfreld-rwmd- 22 ing 486 ,-...andfaisecond-'condenser:4924s in parallel with field Winding 481. Rotor 490 is connected with vsliaft :rpreviously identied.

`ilotorf'rlris :shovvnsto comprise a pair offeld r=windings; 493zandf4l94fand a; squirrelfcage .rotor *495. ',A.icondenser"496yfis in seriesl with Winding :44.93 andia secbndfcondenserrtg'l-is `in parallel-With winding-494. L'Riotor 497: is conneoted-to a shaft 542.

. Motors L350 anc-i3 59 are of a familiar type which :foneratefina rstdirectionfwhen :the ftwo vwindings .areeenergized-l with-.currents in .quadrature yhaving-aarst.-phase relation, and in the opposite di- .rectionfwhenthe .phase relation of the currents ,"irnquadrature is reversed.

,zMotorfa-and regulating network I .are com- -prised infscourseV control unitf I I, Vw=hichalso n- -c1udes..an energizing 'network 505l 'for .a center- :zero pilots iidirectien indicator '508 includedin .inlstrumentipanelflS. 1Network -505 includes alirst .potentiaLd-ividedlSD having'fa winding 507 and-a slider 5I0, and a second potentia1-divider5l I- in- "cludingsawindingf-i .andfaslider 5I 3. `.The posi- .tive terminal .'offzsource-ZE I isfoonnected to Wi-ndvings=5IVI and-,5H by conductors .-52B-.andf-52lz'lthe 4fother ends rofwindings 501L and 5 I I; areconnected lto the .negative termi-naief `source-36| .through conductor l500-fand ground connection l`5 I 4. Me- -.ter 503 is connected between. slider.- 5 I3 and: slider --52I'01:by.conductorsI1 and-5I?)I so that it indicates the potential udiierence between `the sliders. Slider. -5 L3 is connected toshaft 439 for actuation .therebyzf slidenzl'll may fbefmanually operated by afmanual .knob 5-I-8.

Shaftn439 isalso coupled,- through such .reducingsgear. `mechanism 5 I-6 .as .may be necessary, -to actuate A vthe azimuth functionA `of autopilot IIJ. .il-he autopilot Vmay .be ,provided Awith Y a manually operablek-nob 5'I'I.

It will be appreciated that the maximum values 4and the lresistance gradients or variable resistors 356,.. 5I I 23,V M54, .I 63,-and140'l :must ybe chosen with -somediscretion `so that theyfares-in proper accord with one ianotherandgive y.satisfactory ranges Vvof operation. L-I have -found `that a-rangefof 0-350 .P...H..is-desirable imn resistors 5 I.v andy 390; this :isprovidedf .by 230 ol'im.r resistances f traversed. -in ..1f-12..turns.oi .their shafts. Similarlyfa rangerof v.0to miles, desirable.for p resistors I-23 andfll, is .providedby .1320 ohm resistances traversed .in turns .of their. shafts and `a range of- 0 -to 7500 feet, desirableinaTR `nesistors .H53 vand |54. isprovidedby 47 ohmresistors traversed in 31/2 .turns-o. their shafts. Tf resistor 535 giving .a .range-of,-0f-8D;.seconds vvmay Vhave a resistance of ...500-ohms traversedin l0y turns of its-shaft. @ther combinationsof resistancesrmay .of course be Afound satisfactory.

Valuesiorsother .elementsreferred to in -describingA the v7invention thus vtar iare fResisto14'2'5 ohms 400 ResistordZ do 400 Resistor-'S4128 do 1000 Resistor-23429 do 1000 *Resistor 1460 me'gohms 5 Potentiometerl'f' ohms 500 Potentiometer 43 D 1do 1 100 Potentiometerffllal do 500 "Potentiometerll ;do 600 -ACapa'citorrlli'i I -microfarad .25 `Capacito f492 do .2 Capacitor-f 495V do '.25 Capacitorv'l -do '.'2 ASolI-rce'l-I vo'ltsD.. C .28

z.Sourrzeil LvoltsliOO cycles- Operation of navigation system The operation of this phase of the invention will now be explained. Referring first to Figures 4 and 12, in the Zero condition of the instrument each of rate knobs 3d and 4|3 is at the limit of its travel in the low rate direction: this sets the 1" resistors and the R potential dividers to zero and stops the rate motors M1 and M2 by reducing the comparison voltages to zero. Each of displacement knobs |20 and 409 is at the limit of its travel: this sets the p resistors and counters, and also counter |33, at zero. Each of sliders 432, 4333, and 5|3 is at the center of its traverse. Switch 420 is closed and sources 8| and 36|, as Well as the constant voltage sources for the R potential dividers, are energized. Knob |53 of the trail resolver |50 is at the end of its travel, counter 5| is at Zero, and station angle knob |55 and station bearing knob |12 of the trail resolver are set to zero. The compass system is also energized.

By way of a concrete problem let it be assumed that a craft equipped for practicing the invention is approaching airport P, Figure 1, and the pilot wishes to continue from there to drop a cargo carrier for delivery at TX. Let Z1 be 287 miles, Z2 be 233 miles, d1 be 288 miles, and dz be 55 miles. From the map angles a1, and a2 are found to be e3", N 101 E, and N 58 E, and the sector of approach is determined to be Z. Suppose the craft is to ily at an altitude of 7000 feet with an airspeed of 175 miles per hour: for the particular cargo carrier to be used let the trail distance for these conditions be 472 feet. The wind is blowing at 30 miles per hour from N 69 W. Under these conditions it may easily be shown that the craft should pass over P with a heading N 39 E. and will follow a ground path N 48 E.

The instrument is set up as follows. Knobs i3 and 9S controlling the reversing gearing 3|, |21, |35, and |39 are turned to their forward position, for a sector Z approach. Station bearing knob |12 is set to N 161 E. Station angle knob |85 is set to 43. Knob |63 is turned until its graduations, and counter |5|, indicate a trail distance of 472 feet. The components of the trail distance along lines SiTx and SzTx are thereafter continuously compensated for changes in the heading of the craft, by the input to the trail resolver from the compass.

Correlation is also required of the p counters, |35 and 520, with the primary and secondary phase Shifters and oscilloscope pulse pairs in the distance monitor. It will be recalled that with either phase shifter in its zero position the angular displacement between the pulses of the associated oscilloscope pulse pair is a measure of the round trip distance between the aircraft and one of the base stations, and that if the pulses are brought into alignment by adjustment of the phase shifter, the amount of adjustment required is also a measure of the round trip distance.

As the aircraft moves toward its destination, di and d2 become larger. The values of Z1 and Z2 do not change, so the values of p1 and p2 :become smaller. In other words, Ioperation of the counters must be positive in the opposite direc-tion to that of Ithe components in the distance monitor. Since the counters are to be opera-ted by means which also adjust the phase Shifters, it is essential, moreover, that the coupling members IM and 52| be operated `only after a proper relationship between the counters and the position of shafts 33 24 and 35 has been established. This is done at a time -when the phase Shifters and counters can both be related to a location whose primary and secondary radio distances are known.

In the illustrative example given above, Z1 and Zz are 287 miles and 233 miles. At the point P, the values d1 and d2 are 228 miles and 55 miles: p1 and p2 are therefore 59 miles and 173 miles. At the destination Tx, d1 and da are the'same as Z1, and Z2 and p1 and p2 are zero. Accordingly, while d1 is changing from 228 to 287 miles, p1 must change from 59 miles to 0 miles, and While d2 is changing from 55 miles to 233 miles, p2 must change from 173 miles to 0 miles.

One method of coordinating the navigating unit and the distance monitor will now be evident. Counter' |35 is set to 59 miles, and primary phase shifter shaft 33 is rotated to an angle corresponding to 228 miles: counter 52B is similarly set to 173 miles and secondary phase shifter shaft 35 is rotated through an angle corresponding to 53 miles. Now if the aircraft takes such a position that the primary and secondary oscilloscope pulse pairs are in alignment, it is accurately located at P, and coupling units |34 and 52| can beengaged.

The above method involves bringing the aircraft to a particular location, and hence might at times require that it go out of its way to coordinate the instrument. This can be avoided as follows: The phase shifter shafts are set to the radio distance of any point for which these are known, and the p counters are similarly set. Then without waiting for the craft to take any particular position as indicated by the oscilloscope pulse pairs, the coupling units are engaged. Operation of knobs |20 and 409 now adjust the phase shifters and p counters simultaneously, and at any time the pulse pairs can be brought into alignment by this means, the counters then indicating the p values for whatever spot the craft happenrs to be in, and the amounts of adjustment of the phase shifter shafts giving the distances from that spot to the base stations.

The method of setting up and coordinating the instrument has now been explained. However, the aircraft is in flight, and its movement will with respect to the base stations immediately cause the pulse pairs to start moving out of alignment. Manual operation of knobs |20 and 403 will maintain the pulse pairs in alignment if this is desired, or they may be allowed to diverge and so indicate distance of the aircraft from the point for which the units were coordinated.

Due to the limitations set by the selection of suitable resistance values for components of the Wheatstone bridge to give desired sensitivity, the navigating unit is effective only when the craft is within an area limited by the arcs R1, R2, R3, and R4 in Figure 1. When using the computer here described, R1 has the radius Z1-40; R2 has a radius of Z1; R3 has a radius of Zz40; and R4 has a radius Z2. When the monitor indicates that both the primary and the secondary radio distances are less than 40, the navigation unit is ready to use. In brief review, the system is operated by setting up known distances and angles on the navigating unit, coordinating and then coupling the navigating unit with the distance monitor, and thereafter manually operating the rate and displacement knobs so that the oscilloscope pulse pairs are maintained in alignment. This alignment can be obtained only when the counters on the navigating unit indicate p1 and p2 for the location of the aircraft, so that when the pulse pairs remain 

